Contrast enhancement is extensively used in clinical radiology, although the development of contrast material for use in ultrasound has been limited, and no completely satisfactory material is currently available. The ideal ultrasound contrast agent must be safe and highly echogenic, with no evidence of hemodynamic toxicity. Studies were performed to determine the safety and efficacy of a novel fluorocarbon emulsion (qw3600) which has been shown to produce dense myocardial enhancement in dogs. Five groups of two monkeys were imaged following 3 consecutive intravenous injections at five differing dosages. Clinical, hematologic, and hemodynamic parameters were monitored prior to, during, and at 1, 2, and 7 days post-treatment. Results of these studies have shown no significant changes in heart rate, electrocardiograms, or blood pressure (bp) at the lower doses studied. Higher doses resulted in transient reductions in bp which normalized within 30 sec, and transient elevations in lactic dehydrogenase (LDH) and serum glutamic-oxaloacetic transaminase (SGOT) which returned to baseline levels roughly 7 days post-dosing. Overall, no significant hemodynamic effects or cardiovascular toxicity was noted following 3 consecutive administrations at dosages sufficient to consistently produce dense myocardial opacification. Emulsion consistently produced saturable, dose-related enhancement of blood pool and myocardium in monkeys with peak myocardial enhancement at the mid-dose studied.